However, I once worked in the "tube room" of a large hospital that used pneumatic tubes to deliver paperwork throughout the large building. What Heinlein has created here is effectively a tube system for people.

In 1870, Alfred Ely Beach, tried to construct a prototype pneumatic train subway in New York City. The city fathers were not impressed and decided on the elevated train concept instead.

If you want to check out what a factory conveyor belt system for a country would look like, see the entry for rolling roads, from The Roads Must Roll, also by Heinlein.

Also, take a look at a "vacutube" that operates in the vertical dimension for one passenger at a time; see bounce tube, also by Robert Heinlein.